It shows incomplete dominance. In a cross between true-breeding red flowered (RR) and true-breeding white-flowered plants (rr) in F1 generation we get pink (Rr) flowers. When F1 was self-pollinated, we get 1. : 2 : 1 (Red : Pink : White) ratio of flowers. Genotypic ratio was exactly as we would expect, but phenotype ratio had changed from 3 : 1. (dominant: recessive) ratio to 7 : 2 : 1. This is because R was not completely dominant over r and it made it possible to distinguish Rr as pink from RR (red) and rr (white).